In recent years, air conditioning devices for heating, cooling, and the like have become more advanced and widespread. As the residential areas where air conditioners are used grow, the importance of a total heat exchanger for an air conditioner, which can recover the temperature and humidity during ventilation, is increasing. The total heat exchanger as described above has a heat exchange element incorporated therein as an element component that exchanges heat. This heat exchange element can exchange latent heat and sensible heat simultaneously without mixing fresh outside air drawn from the outdoors to indoors during the use of an air conditioner with contaminated air to be discharged from the indoors to outdoors. The heat exchange element is required to have high gas-sealing properties and a high total heat exchange rate. Further, in order to reduce power consumption of an air blowing device (such as a fan or a blower) that circulates an air flow for ventilation and to suppress the operating sound of the total heat exchanger to a low level, the heat exchange element is required to have a low air-flow resistance when each air flow circulates.
A conventional heat exchange element employs a structure in which partition members having gas-sealing properties, heat-transfer properties, and moisture permeability are stacked in multiple layers with a predetermined spacing, where each of the partition members is sandwiched between spacing members having a wave shape in cross section. In an example of the conventional heat exchange element, the partition member is a square flat plate, the spacing member is a wave-shaped plate formed into a triangular wave shape in cross section, and the partition members are stacked with the spacing member sandwiched therebetween in such a manner that the wave-shape direction of the alternate spacing members is turned by 90 degrees. Therefore, fluid paths in two directions, through which a primary air flow and a secondary air flow pass, are formed in every two layers (Patent Literature 1). In this heat exchange element, the spacing member is wave-shaped. Therefore, there is a problem in that the effective area of an air-flow path formed between the partition members becomes small because of the thickness of this wave-shaped plate and further the area in which the partition member and the spacing member are in contact with each other is large; therefore, the effective area of the partition member, which is capable of heat exchange, is small, thereby decreasing the total heat exchange efficiency. Furthermore, because the spacing member is formed of paper or the like, there is a problem in that the cross-sectional shape of the air-flow path can be easily deformed, thereby increasing the air-flow resistance.
Therefore, in recent years, a method has been used, in which a resin molded product is used as a spacing member of a heat exchange element instead of a wave-shaped plate, and a partition member and the resin are integrally molded. With this structure, the degree of flexibility in shape of the heat exchange element is increased, whereby the total heat exchange efficiency is improved and the air-flow resistance is reduced (Patent Literature 2).
However, the method, in which the spacing member is molded integrally with the partition member, has a problem of low adhesiveness of a bonded portion between the partition member and the spacing member. Further, because the partition member can expand and be deformed in high-humidity environment, the bonded portion is required to have an adhesive force sufficient to withstand the deformation.
In recent years, mainly, for the purpose of reducing the amount of air leakage from a total heat exchange element and improving the moisture exchange efficiency, a partition member formed with high density has been developed. This partition member has excellent properties as a partition member of the total heat exchange element, such as low breathability (air permeability) and better moisture permeability. At the same time, this partition member has a feature of a large amount of expansion/contraction, a small number of irregularities on the material surface, and a small number of cavities within the material. Therefore, when such a partition member is used, a sufficient amount of resin cannot enter the cavities within the partition member and a sufficient anchor effect is not obtained in the bonded portion. Consequently, a sufficient bonding strength cannot be obtained. Thus, when the partition member and the resin are integrally molded, they are bonded together immediately after the processing; however, the partition member repeatedly expands/contracts because of a change in temperature and humidity during use, thereby eventually causing the partition member and the spacing member to come off their bonded surface. This blocks an air-flow path and therefore increases the air-flow resistance. As a result, there is a problem of decreasing the total heat exchange efficiency.
As a method for solving this problem, a heat exchange element has been proposed, in which only a spacing member is integrally molded, and thereafter a partition member is affixed to the spacing member with an adhesive or the like (Patent Literature 3).
Another heat exchange element has been proposed, in which a cylindrical, triangular, or other-shaped convex portion is provided on a die for molding a spacing member and a partition member is held by the convex portion and embedded in the spacing member (Patent Literature 4).